switch from opt-in to opt-out for analytics

[jbibla]

Because the user isn't able to opt in.

i think we need to default to some amount of analytics. i am very open to letting users opt out. re: cookies - we should investigate the requirements here more closely.

Originally posted by @jbibla in #1718 (comment)

[faboweb]

This is a prerequesit for removing the pref page

[jbibla]

i am having second thoughts about this. perhaps opt in is best. would like this decision to be informed by our legal counsel.

[fedekunze]

I think GDPR requires opt-in